The present invention relates to the delivery of electrical energy to bodily tissues for therapeutic purposes, and more specifically to devices and methods for treating various disorders resulting from nerve transmissions in the brain.
The use of electrical stimulation for treatment of medical conditions has been well known in the art for nearly two thousand years. Electrical stimulation of the brain and the peripheral nervous system and/or direct stimulation of malfunctioning tissue are generally a completely reversible and non-destructive treatment and holds significant promise for the treatment of many ailments.
Transcranial direct current stimulation (tDCS) is being studied for treatment of a number of conditions, such as improving motor performance in healthy people, improving memory consolidation, accelerating recovery from major stroke and the treatment of migraines, bipolar disease, epilepsy, schizophrenia and major depression. tDCS typically involves the application of low frequency oscillatory currents or weak direct currents (e.g., about 1-2 mA) to modulate the activity of targeted neurons in the brain. Typically, the electrode associated with the positive pole or anode causes an increase in nerve activity while the electrode associated with the negative pole or cathode causes a decrease in nerve activity.
Several generations of neurophysiologic experiments have shown that neurons respond to static (DC) electrical fields by altering their firing rates. Firing increases when the anode is located near the cell body and decreases when the field is reversed. However, when the electrodes are placed on the scalp, the current density produced in the brain is exceedingly small, changing membrane potentials only by a fraction of a millivolt. tDCS typically only influences the area of the brain directly underneath the electrode that is close to the skull and thus is more selective than other methods of brain stimulation. Transcranial direct current stimulation is not “stimulation” in the same sense as transcranial magnetic stimulation or the stimulation of the brain and nerves with conventional techniques. It does not appear to cause nerve cell firing on its own and does not produce discrete effects such as the muscle twitches associated with classical stimulation.
Schizophrenics often have what are called negative symptoms. Negative symptoms include apathy, poor attention, poor grooming habits and poor motivation. These symptoms have been associated with under activity of the frontal lobes, particularly a brain area called the left dorsolateral prefrontal cortex (LDPFC). Positive schizophrenic symptoms such as hallucinations may be associated with over activity in different brain areas, like the temporal cortex. Thus, tDCS may be able to up regulate activity in the left dorsolateral prefrontal cortex while simultaneously decreasing activity in the temporal cortex. This could have a substantial impact on a range of schizophrenic symptoms. For depression, tDCS may be able to up regulate activity in the left dorsolateral prefrontal cortex while simultaneously decreasing activity in the right dorsolateral prefrontal cortex. This will likely have a more robust antidepressant effect.
One of the limitations of current tDCS is that the electric current can only be applied for a limited period of time and at a limited power or voltage because the electrodes will begin to damage the tissue they are in contact with. In light of this, improved systems, devices and methods for the treatment of disorders associated with nerve transmissions in the brain are desired.